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The normal activity of living carbon-containing matter is found tobe about 15 decays per minute for every gram of carbon. This activityarises from the small proportion of radioactive 146 C present with thestable carbon isotope 126 C . When the organism is dead, its interactionwith the atmosphere (which maintains the above equilibrium activity)ceases and its activity begins to drop. From the known half-life (5730years) of 146 C , and the measured activity, the age of the specimencan be approximately estimated. This is the principle of 146C dating used in archaeology. Suppose a specimen from Mohenjodaro givesan activity of 9 decays per minute per gram of carbon. Estimate theapproximate age of the Indus-Valley civilisation. |
| Answer» The normal activity of living carbon-containing matter is found tobe about 15 decays per minute for every gram of carbon. This activityarises from the small proportion of radioactive 146 C present with thestable carbon isotope 126 C . When the organism is dead, its interactionwith the atmosphere (which maintains the above equilibrium activity)ceases and its activity begins to drop. From the known half-life (5730years) of 146 C , and the measured activity, the age of the specimencan be approximately estimated. This is the principle of 146C dating used in archaeology. Suppose a specimen from Mohenjodaro givesan activity of 9 decays per minute per gram of carbon. Estimate theapproximate age of the Indus-Valley civilisation. | |